The Sloan Lens ACS Survey. IV. The Mass Density Profile of Early‐Type Galaxies out to 100 Effective Radii

Abstract

We present a weak-lensing analysis of 22 early-type (strong) lens galaxies, based on deep HST images obtained as part of the Sloan Lens ACS Survey. Using advanced techniques to control systematic uncertainties, we show that weak-lensing signal is detected out to $300 h À1 kpc (at the mean lens redshift z ¼ 0:2). We analyze blank control fields from COSMOS in the same manner, inferring that the residual systematic uncertainty in the tangential shear is less than 0.3%. A joint strong-and weak-lensing analysis shows that the average total mass density profile is consistent with isothermal (i.e., / r À2 ) over two decades in radius (3Y300 h À1 kpc, approximately 1Y100 effective radii). This finding extends by over an order of magnitude in radius previous results, based on strong lensing and/or stellar dynamics, that luminous and dark components ''conspire'' to form an isothermal mass distribution. In order to disentangle the contributions of luminous and dark matter, we fit a two-component mass model (de Vaucouleurs+NFW) to the weak-and strong-lensing constraints. It provides a good fit to the data with only two free parameters: (1) the average stellar mass-to-light ratio M Ã /L V ¼ 4:48 AE 0:46 h M L À1 (at z ¼ 0:2), in agreement with that expected for an old stellar population; (2) the average virial mass-to-light ratio M vir /L V ¼ 246 þ101 À87 h M L À1 . Taking into account the scatter in the mass-luminosity relation, the latter result is in good agreement with semianalytical models of massive galaxy formation. The dark matter fraction inside the sphere of radius, the effective radius, is found to be 27% AE 4%. Our results are consistent with galaxy-galaxy lensing studies of early-type galaxies that are not strong lenses, in the 30Y 300 h À1 kpc radius range. Thus, within the uncertainties, our results are representative of early-type galaxies in general.

The mass profile of early-type galaxies in overdense environments: the case of the double source-plane gravitational lens SL2SJ02176-0513

“…The number obtained with the informative M * prior is consistent with local estimates from the SLACS survey (e.g. Gavazzi et al 2007;Bolton et al 2008b), where typically ∼30% of the projected mass inside the effective radius is found to be in the form of dark matter, independent of any assumption on the stellar populations. The broad prior yields a much smaller number, which is hard to reconcile with other observations.…”

“…The measured flux in F814W band was converted into an absolute rest frame V band luminosity of L V = (1.36 ± 0.08) × 10 11 h −2 70 L . This includes corrections from Galactic extinction (Schlegel et al 1998), the small filter shifting correction to translate z = 0.6459 F814W into a rest frame V band, in nearly the same way as (Gavazzi et al 2007) except that, here we do not apply any passive evolutionary correction to the reference redshift zero epoch. To do so, one could use the relation constrained by Fundamental Plane evolution studies (Treu et al 2001:…”

“…For example, gravitational lensing has been used to demonstrate the presence of dark matter haloes (e.g. Kochanek 1994;Treu & Koopmans 2004), and to test the validity of the universal dark matter haloes predicted by numerical simulations (Navarro et al 1997a;Gavazzi et al 2007). When galaxies fall into an overdense environment, i.e.…”

Total mass distributions of Sersic galaxies from photometry and central velocity dispersion

“…Ferreras et al (2008) suggest a large scatter in the outer slope of the dark matter distributions that they recover for their targeted galaxies. Gavazzi et al (2007) corroborate an NFW modelling of the dark haloes of their sample galaxies, suggesting that the total matter density tends to an overall isothermal form. Given this degree of uncertainty, it might be argued that there is not much sense in splitting hair to decide between an NFW and isothermal dark matter distributions, as long as the dark haloes that we probe in our analysis are compatible with observations or simulations.…”

Multi-band morpho-Spectral Component Analysis Deblending Tool (MuSCADeT): Deblending colourful objects

“…Chang et al 2013;Arneson 2013). In strong gravitational lensing, deblending of the foreground lensing object from the background lensed sources is essential, for example as shown at galaxy scale by Gavazzi et al (2007) and at cluster-scale by Massey et al (2015). This is true for at least two reasons.…”